Wheel Strut for Vehicle Suspension

ABSTRACT

The invention relates to a rubber metal bearing for a wheel suspension of a motor vehicle comprising an elastic rubber body ( 10 ) arranged between an outer bushing ( 8 ) and an inner bushing ( 9 ) aligned coaxially therewith and fastened thereto. The outer bushing ( 8 ) has a front frontal surface ( 11 ) to which at least one front elastic rubber damping element ( 13 ) is attached, and a rear frontal surface ( 12 ) to which at least one rear elastic rubber damping element ( 13 ) is attached, wherein the front and rear rubber damping elements ( 13 ) are arranged asymmetrically to one another.

The present invention relates to a rubber metal bearing for a wheel suspension of a motor vehicle as claimed in the preamble of claim 1, a trapezoidal strut provided therewith as claimed in the preamble of claim 8 as well as a wheel suspension, in particular an independent wheel suspension, as claimed in the preamble of claim 9.

Generic rubber metal bearings are known in many different forms and are used in very different technical fields, when a first component is pivotably fastened to a second component and, at the same time, the transmission of disturbing instantaneous loads or noise caused thereby is to be avoided. Rubber metal bearings are used in very different embodiments, in particular as guide joints on axle suspensions and wheel suspensions of motor vehicles. They have to be able to carry out the pivoting movements of the wheel guiding members, i.e. the wheel guiding struts and the like, said pivoting movements occurring during compression and rebound of the wheels, wherein the elastic rubber body is subjected to shear, and to be able to absorb the vibrations produced on the axle suspension and/or wheel suspension.

Rubber metal bearings are, however, also used in specific embodiments in order to influence additionally the individual steering behavior of a motor vehicle, both during cornering and also during load changes. In the known manner, a tendency to oversteer occurs in most motor vehicles during cornering, as a result of the elasticity present in the wheel suspension under the action of lateral forces on the wheels, and which is generally undesirable. In order to counteract said tendency to oversteer, it is known to use rubber metal bearings of variable flexibility for the linkage on the vehicle body side, for example of a transverse strut, i.e. a wheel guiding strut, the pivot axis thereof running approximately parallel to the longitudinal axis of the vehicle, and to dimension said rubber metal bearings so that the wheel carrier may be pivoted about a substantially vertical axis during cornering, and thus be pivoted in the toe-in direction under the action of the centrifugal and/or lateral forces which occur during cornering.

For example, rubber metal bearings are used for this purpose, said rubber metal bearings being particularly flexible in certain directions under the action of a radial load, due to recesses arranged in the elastic material. Also, embodiments of rubber metal bearings are known which are specifically designed for the forces to be transmitted of oblique struts, i.e. wheel guiding struts, the pivot axes thereof running slightly obliquely to the longitudinal axis of the vehicle, or of longitudinal struts, i.e. wheel guiding struts, the pivot axes thereof running substantially at right angles to the longitudinal axis of the vehicle.

For example, EP 1 216 859 A2 discloses a torsion beam rear wheel suspension for a motor vehicle. The two longitudinal struts forming the torsion beam are articulated to the vehicle body on the body side via in each case a rubber metal bearing. The rubber metal bearings are substantially formed from a cylindrical inner bushing and a cylindrical outer bushing which has a larger diameter than the inner bushing and is arranged coaxially to the inner bushing, wherein an elastomeric element is fixedly inserted between the outside of the inner bushing and the inside of the outer bushing and connects the inner bushing and the outer bushing together in a resilient manner. To limit the lateral mobility of the torsion beam axle, according to one embodiment it is proposed to permit the elastomeric element in the region of the outer frontal surface of the outer bushing to protrude in the axial direction from the rubber metal bearing, such that it forms a continuous axial damping ring (snubber ring) adjacent to the outer frontal surface of the outer bushing and supported on said surface. Said damping ring mounted at the front of the outer frontal surface of the outer bushing defines the axial mobility of the rubber metal bearing in the bearing holder to the outside and as a result the lateral mobility of the torsion beam axle.

Moreover, a rubber metal bearing for mounting the longitudinal struts of a torsion beam axle on a vehicle body is disclosed in EP 1 319 534 A2, comprising an outer bushing with a horizontal portion and a flange portion perpendicular thereto, an elastic main body with a horizontal portion inserted into the outer bushing, which is connected to the horizontal portion of the outer bushing, and a portion which is vertical relative to the horizontal portion, which is connected to the flange portion of the outer bushing, and an inner bushing which is inserted into the main body. To influence the rigidity of the elastic main body, two axial openings are incorporated therein: a first opening in a front portion of the main body from outside to inside and a second opening in a rear portion of the main body from inside to outside. Moreover, the elastic main body is also configured asymmetrically in its vertical portion as well as its horizontal portion. The thickness of the vertical portion is configured to be less in a front region than in a rear region. Moreover, the thickness of an outer portion of the front region of the horizontal main body portion is also less than that of the rear region.

Moreover, wheel suspensions for motor vehicles are known in which specific embodiments of rubber metal bearings for connecting individual wheel suspension components, in particular wheel guiding struts, are used in order to influence positively the toe behavior and/or individual steering behavior of the wheels articulated by a wheel suspension, both during cornering and also during load changes, i.e. generally in the sense of a shift in the toe-in direction.

Thus DE 197 22 650 A1 discloses, for example, a dual wishbone-type suspension system of a rear wheel of a motor vehicle which resolves the problem of longitudinal forces on the suspension system due to uneven road surfaces and wheel braking by distinguishing therebetween, such that a deviation of the wheel alignment (toe) against a longitudinal force due to uneven road surfaces is suppressed, whilst a deviation of the wheel alignment against a longitudinal force due to wheel braking is permitted. To this end, one or more rubber metal bearings by which a transverse strut is articulated to the vehicle body and/or by which a wheel carrier and/or a wheel hub are articulated to the transverse strut have a non-uniform modulus of elasticity in the cross-sectional direction perpendicular to the pivot axis thereof. In order to implement said non-uniform modulus of elasticity, it is proposed to provide the rubber material of the rubber metal bearing with a pair of curved free spaces without elastic material.

An oblique strut-rear wheel suspension of a motor vehicle is also disclosed in U.S. Pat. No. 4,603,882 which effects a toe-in displacement on a rear wheel under a lateral force, a braking force, an engine braking force and an engine drive force. A wheel hub and/or a wheel carrier is articulated to a suspension strut via a ball joint and two rubber metal bearings. In order to effect the toe-in displacement of the wheel carrier under the action of the aforementioned forces, it is proposed to align the longitudinal axes of the two rubber metal bearings such that, according to their arrangement and positional relationship to the ball joint, a toe-in displacement of the wheel carrier takes place under the action of the aforementioned forces. One embodiment provides the arrangement of a stop disk made of relatively hard rubber between an axial end of the rubber metal bearing and a bearing bracket of the transverse strut retaining the rubber metal bearing, so as to permit in this manner the direction of movement of the rubber metal bearing only in one fixed axial direction.

In view of this, the object of the present invention is to provide a rubber metal bearing which is suitable for use as a connecting joint between the wheel guiding struts of a wheel suspension, in particular an independent wheel suspension, of the unarticulated wheels of a motor vehicle such that it permits a specific influence of the toe behavior and/or individual steering behavior of the wheel articulated by the wheel suspension under the action of the forces acting on the wheel and/or the wheel suspension during cornering or load changes. Moreover, the object of the invention is to provide a trapezoidal strut and a wheel suspension, in particular an independent wheel suspension, for the unarticulated wheels of a motor vehicle, which permits the desired individual steering behavior of the vehicle wheel articulated by the trapezoidal strut and/or the wheel suspension, both during cornering and load changes, in particular during braking of the motor vehicle. Moreover, the trapezoidal strut and the wheel suspension are intended to achieve excellent cornering stability of the motor vehicle as well as an accurate reaction to steering inputs and also a long service life and to be able to be produced cost-effectively.

These objects are achieved by a rubber metal bearing having the features of claim 1, by a trapezoidal strut having the features of claim 8 and by a wheel suspension having the features of claim 9. The subclaims reveal further particularly advantageous embodiments of the invention.

Reference is made to the fact that the features set forth individually in the following description may be combined in any technically expedient manner and demonstrate further embodiments of the invention. The description also characterizes and specifies the invention, in particular in combination with the figures.

A rubber metal bearing according to the invention for a wheel suspension of a motor vehicle comprises an elastic rubber body arranged between an outer bushing and an inner bushing aligned coaxially therewith and fastened thereto, in particular vulcanized thereto. The outer bushing has a front frontal surface to which at least one front elastic rubber damping element is attached, and a rear frontal surface to which at least one rear elastic rubber damping element is attached, wherein the front and rear rubber damping elements are arranged asymmetrically to one another.

The term “rubber metal bearing” does not constitute a limitation in the sense of the invention relative to an exclusive use of rubber as the rubber body and metal as the inner and outer bushing. On the contrary, the term “rubber” also encompasses any other rubber-like elastic material, for example dimensionally stable but elastically deformable plastics (elastomers). In a similar manner, the inner and/or outer bushing of the rubber metal bearing, as known per se, may be produced from a metal material but may also comprise any other material, for example plastics, provided the material is suitable for the function as the inner and outer bushings of the rubber metal bearing according to the invention.

A diametric arrangement relative to one another is to be understood as the asymmetrical arrangement of the front and rear rubber damping elements, for example. Within the meaning of the present invention, “diametric” means any point of the front rubber damping element is connected to its corresponding opposing point of the rear rubber damping element via a spatial diagonal, wherein the spatial diagonal extends through the central point of the body of the rubber metal bearing. The central point of the body of the rubber metal bearing will generally correspond approximately to the center of gravity of the body.

The asymmetrical arrangement of the front and rear rubber damping elements provides the rubber metal bearing according to the invention with an asymmetrical behavior in the case where forces, in particular axial forces, act on the front and rear frontal surfaces, for example by a bearing bracket retaining the rubber metal bearing. In a conventional fastening of the rubber metal bearing, for example, to a wheel guiding strut, for example a transverse strut, the rubber metal bearing is retained by means of a fastening means which may be inserted through the inner bushing, for example a bolt or screw. The fastening means in this case is, in turn, retained and fastened by two bearing brackets of the wheel guiding strut surrounding the rubber metal bearing, in a manner known per se. The bearing brackets generally define, therefore, the mobility of the rubber metal bearing in the axial direction and may transmit axial forces to the front and/or rear frontal surface of the outer bushing via the corresponding front and/or rear rubber damping element.

The force acting in the axial direction and axially compressing the rubber metal bearing according to the invention in one direction thus produces a torque on the rubber metal bearing due to the asymmetrical arrangement of the front and rear rubber damping elements relative to one another, i.e. with sufficient elastic compressibility of the rubber bodies in the radial direction the torque results in a rotation of the rubber metal bearing about a spatial axis located perpendicular to the axial and/or longitudinal axis of the rubber metal bearing. This rotatability of the rubber metal bearing may be used for specific control of the toe behavior and individual steering behavior of the wheel connected to the rubber metal bearing via the wheel carrier. In particular, the asymmetrical arrangement of the front and rear rubber damping elements of the rubber metal bearing according to the invention, relative to an arrangement between the wheel guiding strut and the wheel carrier, is selected such that both during cornering and load changes an adjustment of the wheel track generally takes place in the toe-in direction, in particular during braking of the motor vehicle, which generally acts in a stabilizing manner on the driving behavior of the motor vehicle.

According to an advantageous embodiment of the invention, in each case a plurality of front and rear rubber damping elements are arranged spaced apart from one another on the front frontal surface and on the rear frontal surface. As a result, an accurate elasticity and/or rigidity of the rubber metal bearing which is specifically adapted to the desired individual steering behavior is permitted. The total elasticity and/or rigidity which is effective in the axial direction of the front and rear rubber damping elements may be set in a simple manner by the number of elements and the spacing thereof relative to one another.

A further simple possibility for setting the total elasticity and/or rigidity in the axial direction of the rubber damping elements arranged on a frontal surface is to provide the front and rear rubber damping elements with different lengths and/or widths and/or heights. Due to the variable heights of the rubber damping elements, for example, the spring constant of each individual rubber damping element, which acts during compression as a spring, may be set according to the current degree of compression. Such a path-dependent spring constant may also be advantageously achieved by the rubber damping elements being provided with a conical profile. Overall, by the choice of suitable spacings of the rubber damping elements relative to one another and the lengths and/or widths and/or heights thereof as well as their profiles, the elasticity and/or rigidity acting in the axial direction may be varied both independently of the path and dependent on the path, i.e. taking account of the actual degree of compression.

According to a further advantageous embodiment of the invention, the front rubber damping elements are arranged in a front peripheral portion of the front frontal surface and the rear rubber damping elements are arranged in a rear peripheral portion of the rear frontal surface, wherein the front peripheral portion and the rear peripheral portion in each case form a maximum of half of the corresponding total frontal surface and the front peripheral portion is arranged diametrically to the rear peripheral portion. As a result, it is ensured that the rubber metal bearing, as described above, may rotate under the action of the torque by a specific angle transversely to the longitudinal axis of the bearing as, for example, the region exactly opposing the front peripheral portion (not the diametrically opposing region) of the rear frontal surface has no rubber damping elements and thus sufficient free space remains between this region of the frontal surface and a bearing bracket for a rotation of the rubber metal bearing. The rotation, however, requires a certain elastic compressibility of the rubber body in the radial direction. Such a radial compressibility may, for example, be provided by the means known per se from the prior art and already mentioned in the introduction.

For particularly simple and cost-effective manufacture, the front and rear rubber damping elements are configured integrally with the rubber body, according to a further advantageous embodiment of the invention. Expediently, in this case the front and rear rubber damping elements are connected to the rubber body via a relatively narrow rubber web, so that, for example, they may be folded over for easier insertion of the rubber body into the outer bushing.

An advantageous, immediate response of the rubber metal bearing according to the invention to an alteration in the direction of the vehicle or an acceleration and/or deceleration/braking procedure is achieved by the front and rear rubber damping elements being already substantially arranged in the unloaded state of the rubber metal bearing without clearance between the front frontal surface and/or the rear frontal surface and a corresponding bearing bracket retaining the rubber metal bearing. The immediate and accurate response to steering inputs results in a substantial contribution to effective cornering stability of the motor vehicle. In addition to the front and rear rubber damping elements bearing without clearance on the bearing bracket, a pretensioning force compressing the rubber damping elements may also be applied to the rubber metal bearing in the installed state. As a result, already in a normal installed state, a certain twisting of the rubber metal bearing according to the invention in the toe-in direction may be achieved.

A further advantageous embodiment of the invention provides that the front and rear frontal surfaces are in each case of flange-like configuration and extend approximately at right-angles to the longitudinal axis of the rubber metal bearing. Thus, the front and rear frontal surfaces may be designed according to the axial forces to be received thereby when used in a wheel suspension and/or a wheel guiding strut. Also, a frontal surface of correspondingly wide design simplifies the arrangement and fastening of the rubber damping elements in comparison with a frontal surface which substantially only corresponds to the thickness of the sleeve material. Moreover, the flange-like frontal surface may also serve as an axial limit for a component to be connected to the outer sleeve, for example a wheel carrier and a wheel hub.

A wheel guiding strut according to the invention, in particular a trapezoidal strut, for a wheel suspension of a motor vehicle comprises two connecting points on the vehicle body side for connecting the trapezoidal strut to a vehicle body or an auxiliary frame connected to the vehicle body, and two connecting points on the wheel carrier side for connecting a wheel carrier, wherein at least the rear bearing in the direction of travel, on the wheel carrier side, is a rubber metal bearing, as set forth in the accompanying claims 1 to 7 and the description. The trapezoidal strut according to the invention provides the substantial advantage that a bearing normally used as a rear ball and socket joint on the wheel carrier side, for connecting the wheel carrier, may be dispensed with and may be replaced by the rubber metal bearing according to the invention. As rubber metal bearings are able to be produced more cost-effectively in comparison with ball and socket joints, cost advantages may be achieved by the trapezoidal strut according to the invention.

The individual steering behavior of the trapezoidal bearing may be set in a simple manner by the rubber metal bearing according to the invention, as already described above. A rotation of the rubber metal bearing according to the invention transversely to its longitudinal axis leads to a rotation of the entire trapezoidal strut about a rotational axis substantially perpendicular to the extension plane of the trapezoidal strut, enabling a toe displacement of the wheel carrier connected to the trapezoidal strut. The trapezoidal strut according to the invention provides the further advantage relative to the use of a ball and socket joint that by means of the rubber metal bearing according to the invention an adjustment in the toe-in direction is also possible even during a braking process of the motor vehicle, which is not possible with a ball joint which is rigid per se. Moreover, the trapezoidal strut according to the invention permits excellent cornering stability for the motor vehicle.

Moreover, a wheel suspension according to the invention, in particular an independent wheel suspension for the unarticulated wheels of a motor vehicle, comprises a wheel carrier, which via at least one wheel guiding strut, in particular a trapezoidal strut described above, is articulated to a vehicle body or an auxiliary frame connected to the vehicle body. For connecting the wheel carrier to the wheel guiding strut, at least one rubber metal bearing is provided as set forth in the accompanying claims 1 to 7 and the description. The alignment and arrangement of the rubber metal bearing according to the invention is such that the front frontal surface of the rubber metal bearing is arranged in the direction of travel and the rear frontal surface is arranged counter to the direction of travel.

In this manner, the wheel suspension according to the invention permits specific influence on the toe behavior and/or individual steering behavior of the wheel articulated by the wheel suspension, under the action of forces acting on the wheel and/or the wheel suspension during cornering or load changes. Moreover, excellent cornering stability is provided as well as an accurate reaction to steering inputs and additionally a long service life and the ability to be produced cost-effectively.

Further advantageous details and effects of the invention are described hereinafter with reference to exemplary embodiments shown in the drawings, in which:

FIG. 1 shows a schematic plan view of a wheel guide carrier according to the invention which comprises a rubber metal bearing, also according to the invention,

FIG. 2 shows two cross-sectional views of a first exemplary embodiment of a rubber metal bearing according to the invention,

FIG. 3 shows a cross-sectional view of a second exemplary embodiment of a rubber metal bearing according to the invention,

FIG. 4 shows a cross-sectional view of a third exemplary embodiment of a rubber metal bearing according to the invention,

FIG. 5 shows a front view of a rubber damping element of the rubber metal bearing of FIG. 4 and

FIG. 6 shows a graphical representation illustrating the torque path depending on a rotation of a rubber metal bearing according to the invention in the toe-in and toe-out directions.

In the various figures, the same parts are always provided with the same reference numerals, so that said parts are generally only described once.

FIG. 1 shows a schematic plan view of a wheel guide strut 1 according to the invention. The installation position shown is illustrated by an arrow 2 in the direction of travel of a vehicle, not shown. In the exemplary embodiment shown, the wheel guide strut 1 is a torsionally rigid transverse strut and/or trapezoidal strut which comprises two connecting points 3 on the body side for connecting the trapezoidal strut 1 to a vehicle body, also not shown in FIG. 1, or an auxiliary frame connected to the vehicle body. The connecting point 3 on the left-hand side of the body shown in FIG. 1 is a front internal connecting point 3 viewed in the direction of travel 2, whilst the right-hand connecting point 3 represents a rear internal connecting point 3.

Moreover, the wheel guiding and/or trapezoidal strut 1 also comprises two connecting points 4 on the wheel carrier side, for connecting a wheel carrier 5. The wheel carrier 5 is shown merely symbolically in FIG. 1. Similar to the connecting points 3 on the body side, the connecting points 4 on the wheel carrier side may also be differentiated as a front outer connecting point 4 on the wheel carrier side viewed in the direction of travel 2 (left connecting point 4 in FIG. 1) and a rear outer connecting point 4 on the wheel carrier side (right connecting point 4 in FIG. 1). In the exemplary embodiment shown in FIG. 1, at least the rear connecting point 4 on the wheel carrier side comprises a rubber metal bearing 6 according to the invention and described therein. A first exemplary embodiment of the rubber metal bearing 6 is described hereinafter with reference to FIG. 2.

In FIG. 2, two cross-sectional views of a first exemplary embodiment are shown of a rubber metal bearing 6 according to the invention. The left-hand view shows a section through the rubber metal bearing 6 along its longitudinal axis 7, which at the same time coincides with the X-axis of the three coordinate axes X, Y, Z indicated in FIG. 2. The right-hand view of FIG. 2 shows the rubber metal bearing 6 in a cross-sectional view perpendicular to the X-axis and/or longitudinal axis 7 along the cutting line A-A shown in the left-hand view.

In the longitudinal section of the rubber metal bearing 6, an outer bushing 8 and an inner bushing 9 aligned coaxially therewith may be seen clearly. Between the outer bushing 8 and the inner bushing 9 an elastic rubber body 10 is fastened, for example the rubber body 10 is vulcanized to the outer bushing 8 and the inner bushing 9 in a manner known per se. Moreover, the outer bushing 8 comprises both a front frontal surface 11 as well as a rear frontal surface 12 which, as may be clearly derived from FIG. 2, in the exemplary embodiment shown in each case are of flange-like configuration and extend substantially approximately at right-angles to the longitudinal axis 7 of the rubber metal bearing 1. As also may be seen in FIG. 2, at least one elastic front rubber damping element 13 is attached to the front frontal surface 11 and at least one elastic rear rubber damping element 13 is also attached to the rear frontal surface 12. The front and rear rubber damping elements 13 are arranged asymmetrically relative to one another. In the first exemplary embodiment shown, the front and rear rubber damping elements 13, in particular, are arranged diametrically to one another, so that the rubber metal bearing 1 on its frontal surfaces 11 and 12 has an asymmetrical construction.

In the right-hand cross-sectional view of FIG. 2, a front peripheral portion of the front frontal surface 11 may be clearly seen, in which a plurality of elastic front rubber damping elements 13 are arranged. The front peripheral portion extends, as may be seen in the cross-sectional view, in the half of the front frontal surface 11 extending to the left from the Z-axis shown. It comprises, in the exemplary embodiment shown, approximately half of the entire frontal surface 11. Thus, the left-hand half of the front frontal surface 11 shown forms the front peripheral portion in which the elastic front rubber damping elements 13 are arranged. The right-hand half of the front frontal surface 11 does not contain any front rubber damping elements 13.

As may also be derived from the right-hand cross-sectional view of FIG. 2, in the exemplary embodiment shown, a total of four individual rubber damping elements 13 spaced apart from one another are arranged in the front peripheral portion of the front frontal surface 11. The damping properties, in particular the total elasticity and/or rigidity which is effective in the axial direction of the front rubber damping elements 13 arranged in the front peripheral portion of the front frontal surface 11, may be accurately set by the number of front rubber damping elements 13 and their spacing from one another.

The rear frontal surface 12 comprises, similar to the front frontal surface 11, a rear peripheral portion in which the rear rubber damping elements 13 are arranged, wherein the rear peripheral portion is arranged diametrically to the front peripheral portion. The diametric arrangement of the front peripheral portion of the front frontal surface 11 to the rear peripheral portion of the rear frontal surface 12 means, in the exemplary embodiment shown in FIG. 2, that the rear frontal surface 12 which is not visible in the right-hand view of FIG. 2 has a mirror-inverted arrangement of the rubber damping elements 13 of the frontal surface 11 relative to the Z-axis. Accordingly, the rear peripheral portion of the rear frontal surface 12 in which the rubber damping elements 13 are arranged makes up approximately half of the entire rear frontal surface 12, wherein said rear peripheral portion is arranged in the right-hand view of FIG. 2 to the right of the Z-axis. The diametric asymmetrical arrangement is visible in the left-hand view of FIG. 2, in which a front rubber damping element 13 of the front frontal surface 11 is shown top left and a further rear rubber damping element 13 of the rear frontal surface 12 is shown bottom right.

It may also be derived from the left-hand view of FIG. 2 that the rubber damping elements 13 in the exemplary embodiment exhibit a conical profile. Due to the steepness of the profile flanks and the size of the cross-sectional surface of the individual rubber damping elements 13, additionally the spring constant of each individual rubber damping element 13 acting as a spring during compression may be substantially set, whereby a desired response behavior of the rubber metal bearing 6 according to the invention to axial forces may be set. It is generally the case that the more pointed the conical shape of each individual rubber damping element 13, the lower its spring constant, in particular at the start of the compression. The lower the spring constant of the rubber damping elements 13, the more flexibly the rubber metal bearing 6 according to the invention reacts to axial forces, i.e. the smaller the torque 14 initially produced about the Z-axis by the axial force acting, for example, in the direction of travel 2, and the asymmetrical arrangement of the front and rear rubber damping elements 13.

Also able to be derived from the left-hand view of FIG. 2 are a left-hand, front bearing bracket 15 viewed in the direction of travel 2, and a right-hand, rear bearing bracket 16 viewed in the direction of travel 2 of the trapezoidal strut 1 shown in FIG. 1. By means of the bearing brackets 15, 16, the rubber metal bearing 6 is retained and fastened to the trapezoidal strut 1 in a manner known per se, for example by means of a bolt or a screw which is inserted through the inner bushing 9 and is retained by the bearing brackets 15, 16. In the exemplary embodiment shown in FIG. 2 of the rubber metal bearing 6, the front and rear rubber damping elements 13 in the mounted, unloaded state are arranged substantially without clearance between the frontal surfaces 11, 12 and the corresponding bearing brackets 15 and/or 16. As a result, an immediate response behavior of the rubber metal bearing 6 according to the invention is advantageously achieved with an alteration to the direction of the vehicle or an acceleration and/or deceleration/braking procedure. An immediate and accurate response to steering inputs provides a substantial contribution to effective cornering stability of the motor vehicle.

In FIG. 3, a cross-sectional view of a second exemplary embodiment of a rubber metal bearing 17 according to the invention is shown. The rubber metal bearing 17 shown differs substantially from the rubber metal bearing 6 shown in FIG. 2 in that at least two front rubber damping elements 13, 18 of different heights in the axial direction of the rubber metal bearing 17 are attached to the front frontal surface 11, and at least two rear rubber damping elements 13, 18 of different heights in the axial direction of the rubber metal bearing 17 are attached to the rear frontal surface 12. The front and rear rubber damping elements 13 and the front and rear rubber damping elements 18 have the same height in pairs, wherein the rubber damping elements 13 and 18, having in each case the same height, are arranged asymmetrically to one another on the front and rear frontal faces 11 and 12. The front and rear rubber damping elements 18 have, in comparison with the front and rear rubber damping elements 13, a shorter height in the axial direction of the rubber metal bearing 17. The front and rear rubber damping elements 13 have a height such that, in the installed state of the rubber metal bearing 17, they bear substantially without clearance on the respective front and rear bearing brackets 15 and/or 16. The front and rear rubber damping elements 18, however, have a certain spacing from the corresponding bearing brackets 15 and/or 16, in the installed state of the rubber metal bearing 17. Thus the rubber metal bearing 17 will behave in a similar manner to the rubber metal bearing 6 with the application of an axial force on the rubber metal bearing 17, i.e. rotate in the direction denoted by 14.

The variable spacing of the front and rear rubber damping elements 13 and/or 18 from the bearing brackets 15 and 16 may alternatively or additionally also be produced by the bearing brackets 15 and 16, as indicated in FIG. 3, having different spacings from the front and rear rubber damping elements 13 and 18. To this end, the bearing brackets 15 and 16 in the region of the front and rear rubber damping elements 13 are accordingly closer to the rubber damping elements 13 than to the front and rear rubber damping elements 18, from which they have a certain spacing.

In FIG. 4, a cross-sectional view is shown of a third exemplary embodiment of a rubber metal bearing 19 according to the invention. In the rubber metal bearing 19, both the front and the rear rubber damping elements 13 are configured in each case as a rubber ring 20. The rubber ring 20 has an asymmetrical axial rigidity. As may be seen in FIG. 5, in which the rubber ring 20 of the rubber metal bearing 19 of FIG. 4 is shown in front view, the asymmetrical axial rigidity in the exemplary embodiment shown in FIG. 4 is achieved by the width of the rubber ring not being constant along its periphery. As may be derived further from FIG. 4, the front rubber damping element 20 and the rear rubber damping element 20 of the rubber metal bearing 19 are also arranged asymmetrically to one another. In FIG. 4, the front (left) rubber damping element 20 is arranged such that in FIG. 4 it has a substantially greater width at the top than at the bottom. The rear (right) rubber damping element 20, however, has a substantially greater width at the bottom than at the top. In this manner, the rubber metal bearing 19 behaves in a similar manner to the already-described rubber metal bearings in the presence of a force acting in the axial direction on the rubber metal bearing 19, i.e. it will rotate in the direction denoted by 14.

FIG. 6 shows a graphical representation for illustrating the torque path, depending on a rotation of a rubber metal bearing according to the invention in the toe-in and toe-out directions. The abscissa 24 of the Cartesian coordinate system shown represents in the positive direction, i.e. in FIG. 6 to the right, the amount of cardanic rotation of a rubber metal bearing according to the invention which is effective for a toe-in movement and in the negative direction (left) the amount of cardanic rotation of the rubber metal bearing according to the invention which is effective for a toe-out movement. The ordinate 21 represents the effective torque produced by the rubber metal bearing, depending on the rotation of the rubber metal bearing. As may be seen in FIG. 6, both the curve 22 for asymmetrical rigidity and the curve 23 for asymmetrical pretensioning provide less torque for toe-in than for toe-out. In other words, the rubber metal bearing according to the invention is displaced more easily in the toe-in direction than the toe-out direction when an axial force is applied, which produces a torque on the rubber metal bearing. The curve 22 corresponds to a rubber metal bearing according to the invention with one respective front and rear rubber damping element which in each case have an asymmetrical axial rigidity, as has been described herein with reference to the third exemplary embodiment of the rubber metal bearing 19. The curve 23 corresponds to a rubber damping element according to the invention which, in addition to the asymmetrical arrangement of the front and rear rubber damping elements, is also pretensioned in the toe-in direction. This may be achieved by the front and rear rubber damping elements 13 of the rubber metal bearing 6 and/or 17 according to the invention in contact with the bearing brackets 15 and 16 in the installed state already being slightly compressed and/or pretensioned by the bearing brackets 15, 16.

The rubber metal bearing according to the invention and disclosed herein, the trapezoidal strut and the wheel suspension are not limited to the embodiments disclosed herein but in each case also encompass further embodiments which act in the same manner. Thus the rubber body may also be bonded, pressed or positively inserted between the inner and outer bushings. Similarly, the rubber damping elements of a peripheral portion of the front and/or rear frontal surface may also have different lengths and/or widths and/or heights as well as different conical profiles and/or cross sections.

In a preferred embodiment, the rubber metal bearing according to the invention is used in a trapezoidal strut having two connecting points on the vehicle body side for connecting the trapezoidal strut to a vehicle body or an auxiliary frame connected to the vehicle body and having two connecting points on the wheel carrier side for connecting a wheel carrier, wherein the rubber metal bearing according to the invention, at least on the rear connecting point on the wheel carrier side, produces the articulated connection between the trapezoidal strut and a bearing of the wheel carrier. Such a trapezoidal strut is preferably used in an independent wheel suspension for the unarticulated wheels of a motor vehicle for connecting a wheel carrier.

LIST OF REFERENCE NUMERALS

1 Wheel guiding strut

2 Arrow in direction of travel

3 Connecting point of 1 on body side

4 Connecting point of 1 on wheel carrier side

5 Wheel carrier

6 Rubber metal bearing

7 X-axis, longitudinal axis of 6

8 Outer bushing

9 Inner bushing

10 Rubber body

11 Front frontal surface of 8

12 Rear frontal surface of 8

13 Rubber damping elements

14 Torque

15 Front bearing bracket

16 Rear bearing bracket

17 Rubber metal bearing

18 Rubber damping elements

19 Rubber metal bearing

20 Rubber ring

21 Ordinate

22 Curve for asymmetrical rigidity

23 Curve for asymmetrical pretensioning

24 Abscissa 

1. A rubber metal bearing for a wheel suspension of a motor vehicle comprising an elastic rubber body (10) arranged between an outer bushing (8) and an inner bushing (9) aligned coaxially therewith and fastened thereto, wherein the outer bushing (8) has a front frontal surface (11) to which at least one front elastic rubber damping element (13) is attached, and a rear frontal surface (12) to which at least one rear elastic rubber damping element (13) is attached, wherein the front and rear rubber damping elements (13) are arranged asymmetrically to one another.
 2. The rubber metal bearing as claimed in claim 1, wherein in each case a plurality of front and rear rubber damping elements (13), spaced apart from one another, are arranged on the front frontal surface (11) and on the rear frontal surface (12).
 3. The rubber metal bearing as claimed in claim 1 or 2, wherein the front and rear rubber damping elements (13) in each case have different lengths and/or widths and/or heights.
 4. The rubber metal bearing as claimed in one of the preceding claims, wherein the front rubber damping elements (13) are arranged in a front peripheral portion of the front frontal surface (11) and the rear rubber damping elements (13) are arranged in a rear peripheral portion of the rear frontal surface (12), wherein the front peripheral portion and the rear peripheral portion in each case form a maximum of half of the corresponding total frontal surface (11, 12) and the front peripheral portion is arranged diametrically to the rear peripheral portion.
 5. The rubber metal bearing as claimed in one of claims 1 to 3, wherein at least two front rubber damping elements (13, 18) of different heights are attached to the front frontal surface (11) and at least two rear rubber damping elements (13, 18) of different heights are attached to the rear frontal surface (12), wherein the front and rear rubber damping elements (13, 18) in each case have the same height in pairs and the rubber damping elements (13, 18) of the same height are arranged asymmetrically to one another on the front and rear frontal surfaces (11, 12).
 6. The rubber metal bearing as claimed in one of claims 1 to 3, wherein the front rubber damping element (13) and the rear rubber damping element (13) are configured in each case as a rubber ring (20), wherein the rubber ring (20) has an asymmetrical axial rigidity.
 7. The rubber metal bearing as claimed in claim 6, wherein the width of the rubber ring (20) is not constant along its periphery.
 8. A trapezoidal strut for a wheel suspension of a motor vehicle comprising two connecting points (3) on the vehicle body side for connecting to a vehicle body or an auxiliary frame connected to the vehicle body and two connecting points (4) on the wheel carrier side for connecting a wheel carrier (5), wherein at least the bearing to the rear in the direction of travel on the wheel carrier side is a rubber metal bearing as claimed in one of the preceding claims.
 9. A wheel suspension, in particular an independent wheel suspension for the unarticulated wheels of a motor vehicle having a wheel carrier (5) which is articulated via at least one wheel guiding strut (1) to a vehicle body or an auxiliary frame connected to the vehicle body, wherein for attaching the wheel carrier (5) to the wheel guiding strut (1) at least one rubber metal bearing (6) is provided as claimed in one of claims 1 to
 7. 10. The wheel suspension as claimed in claim 9, wherein the wheel guiding strut (1) is a trapezoidal strut as claimed in claim
 8. 